A cohort of anti-HIV positive donors and controls has been under prospective followup since 1985. The original analysis of the study was published in the New England Journal of Medicine (1989; 321:917). A reanalysis of the data 10 years after study initiation is in progress. At enrollment, 182 subjects were Western blot (WB) positive, including 158 asymptomatic donors (87%), 9 sexual partners of these donors (5%), and 15 persons infected by blood transfusion (8%). In addition, we enrolled a control population consisting of donors who were anti-HIV reactive on the screening enzyme immunoassay but were WB negative (70) or were WB indeterminate (21). Of the WB-positive participants 79 (43%) have MDS. Of those with MDS, 51(65%) have died. The death rate could be higher because some MDS cases are lost to followup. The remaining 103 (57%) of those who are WB positive have to our knowledge not developed MDS, but 60 are lost to followup and 4 died of unrelated causes. Thirty-nine MDS- free patients remain in active followup and can be studied regarding factors that favor long-term survival in HID infection. AIDS or HIV- related phenomena have not developed in any of the 21 WB indeterminate or 70 WB negative subjects.